·
Electrical conduits shall not run in
column.
·
Earth work excavation for basement above
3 m should be stepped form.
·
Any back filling shall be compacted 95%
of dry density at the optimum moisture content and in layers not more than
200mm for filling above structure and 300 mm for no structure.
·
f soling is specified the soling stones
shall be laid at45° to 60° inclination (and not vertical) with interstices
filled with sand or moorum.
·
y represents tor steel grade - fe-415
of IS:1786. With characteristic yield
strength of 415 n/mm minimum.
·
∅
represents mild steel grade - 1 of IS: 432 (part-1).
·
All reinforcement shall be free from
mill scales, loose rust & coats of paints, oil or any other substances.
·
By providing proper cover blocks,
spacers, chairs etc. All reinforcement shall be placed and maintained in
position as shown in structural drawing.
·
Cement shall be 43 grades ordinary Portland
cement conforming to is: 8112 or53 grade ordinary Portland cement conforming to
is: 12269-1987.
·
Cement shall be stored in dry places on
a raised platform about 200mm above floor level and 300mm away from walls. Bags
to be stacked not more than 10 bags high in such a manner that it is adequately
protected from moisture and contamination.
·
Water used for both mixing and curing
shall be clean and free from injurious amounts of oils, acids, alkalis, salts,
sugar and organic materials or other substances that may be deleterious to
concrete or steel. The pH shall be generally between 6 and 8.
·
Cement shall be tested for its setting.
1. The initial setting time shall not be less than
30 minutes.
2. The final setting time shall not be more than 10 hours.
·
Samples from fresh concrete shall be
taken and at least a set of 6 cubes of 150mm shall be prepared and cured. 3cube
each at 7 days and 28 days shall be tested for compressive strength. The test
results should be submitted to engineer for approval. If results are
unsatisfactory necessary action/rectification/remedial measures has to be exercised.
·
A set of cube tests shall be carried out
for each 30 cum of concrete / each level of casting / each batch of cement.
·
Water cement ratio for different grades
of concrete shall not exceed 0.45 for m20 and above and 0.50 for m10 / m15
contractor / mix designer to carry out the necessary initial (preliminary)
tests. For concrete grades m20 and above approved admixture shall be used as
per mix design requirements.
CONCRETE COVER
Clear cover to main reinforcement in
1. Footings: 50 mm
2. Raft foundation. Top: 50 mm
3. Raft foundation. Bottom/sides : 75 mm
4. Strap beam: 50 mm
5. Grade slab: 20 mm
6. Column: 40 mm
7. Shear wall: 25 mm
8. Beams: 25 mm
9. Slabs: 15 mm
10. Flat slab: 20 mm
11. Staircase: 15 mm
12. Retaining wall: 20/ 25 mm on earth
13. Water retaining structures: 20 / 30 mm
·
Contractor shall allow for independent
testing of reinforcement steel for each dia of bar for every 50t and at change
of source.
·
All beam reinf. to be anchored for a
minimum length of 46 x dia of bar into col / supporting beam u.n.
·
Binding wires shall be 16 gauge 1.6mm
soft annealed steel wires free from rust and other contaminants.
Concrete design mix report.
1. Concrete design mix report along with the test results
for concrete cubes shall be submitted in advance for approval before relevant
concreting and the minimum cement content shall be not less than 300 kg/m
2. Slump shall be 100 + 25mm.
·
Pouring of concrete. No concreting
operation shall be carried out during inclement weather conditions like heavy
rain, storm and high winds.
REPAIRS
·
Concrete repairs in any structural
elements shall be carried out only after inspection and as per the approved
method. Contractor to submit detail method statement for engineer's review and response.
·
Concrete floor screed shall be in panels
of 3m x 3m with joints sealed with sealant to match with joints in slab.
Locations to be approved by engineer prior to concreting.
·
All concreting must stop at a shuttered
surface only.
·
At all construction joints the
reinforcement shall be continuous.
·
Construction joint in retaining walls
& water tank shall be provided with an approved sealant.
·
all deeper excavation below the ground
level slab shall be retained by a localized soil and water retention system, as
may be retained by a localized soil and water retention system, as may be
·
dewatering by suitable means to be
adopted (ensuring no fines are drawn out) to keep the founding strata
completely dry and shall be continued until the ground floor slab / beams are cast
and cured to achieve specified design strength.
·
Cement proportion: concrete mix in above
such foundations shall contain 10percent extra cement than specified.
·
At locations of isolation / expansion
joint provide polysulphide sealant with backer rod polystyrene boards.
·
No through bolts shall be used in
formwork of retaining wall. And water tank walls.
FOUNDATIONS
·
All loose pockets and soft spots are to be
filled in mass concrete of grade m10.
·
Back filling behind the retaining wall
shall be carried out only after the ground floor slab is cast and has attained
design strength.
·
The space between hard strata (to
achieve a minimum of 25 met/m2) and bottom of raft/ foundation shall be filled with
plum concrete.
·
Size stone masonry shall be in cm 1:6
unless specified otherwise.
·
Continuous wall foundation shall be
stepped in a ratio of 1 vertical to 2 horizontal wherever level changes are necessary.
·
Sloped portion to be finished smooth
with trowel without using mortar. Column portion to be finished smooth with concrete.
·
Grade of concrete shall be as per
footing schedule/ raft details.
SUPER STRUCTURE
·
All exposed corners of columns and beams
shall have straight edges and shall be champhered if specified in architectural
drawings.
·
Concreting of columns, beams, facials,
and thin sections of concrete members shall be carried out using approved plasticizer
as per manufacturer’s specifications.
·
Concrete pouring, testing, removal of
formwork and acceptance criteria shall be as per relevant Indian standard code
of practice.
·
Centering of cantilever beams and slab
projections shall not be removed unless roof slab above is cast and cured and
sufficient balancing load is attained. Provide pre camber to cant. beams/slabs
·
Before pouring floor level concrete, the
floor systems below shall be sufficiently supported by means of propping and
this system shall be approved by the engineer-in-charge.
·
Concrete in toilet, kitchen, water body
areas shall be mixed with approved waterproof compound and waterproofing over
slabs and sides of walls shall be done as per architectural details.
·
Contractor shall check all the openings
as per architectural/service drawings and shall provide necessary trimming
bars.no additional opening shall be drilled in the structure unless approved.
·
Concrete should be placed in thin layers
which can be effectively compacted as the placing proceeds say in 300mm.
·
When casting columns, walls or beams of
depth 700mm or more, a layer of rich cement mortar should be placed first. This
is to avoid accumulation of gravel in the bottom layer and to have a better
bond.
·
Compaction of concrete shall be done by
mechanical vibrators. Proper care shall be taken to avoid segregation and
honeycombing.
·
Contractor shall submit shop drawings
including bar bending schedule for approval prior to taking up of construction.
·
The secondary beam bars shall be placed
over main beam bars when the depth of beams is same at junctions.
·
Short span steel shall be at bottom
layer in two way slab system and spacers bar, chairs to top steel shall be provided
with adequate cover.
·
No splicing of bars shall be made at the
point of maximum tensile stresses.
·
For splices of reinforcement, minimum
lap length for bars shall be 50 x dia of bar.
·
Not more than 1/3 of main reinforcement
shall be lapped at any section.
·
Splices if un avoidable, must be located
from face of the column at not closer than twice the beam depth.
·
Splices in beams shall be contained by
additional stirrups at a spacing not exceeding 150mm over the entire length of
splices.
·
Stirrups shall be closed type with ends
hooked at 135 with 10x bar dia extension (but not less than 75mm).
·
Spacing of stirrups shall not exceed
200mm.
COLUMNS
·
Concrete mix shall be as per schedule of
columns.
·
p.v.c cover blocks to be used with prior
approval of engineer.
·
Rings to be provided for full length of
main rods to prevent dislocation of main bars while concreting, at spacing as
specified in the schedule.
·
Ld. shall be
1.
M25 and above 46 x dia
·
Column starter to be set by template and
shall be provided with next higher grade of concrete mix of columns.
·
Beam bottom levels are to be marked on
column rods and column to be stopped at this level to avoid extra shuttering of
columns below beam bottoms.
DESHUTTERING TIME
·
In normal circumstances where ambient
temp. does not fall below 15 c & where ordinary Portland cement is used
& adequate curing is done. Following stripping time may deem to satisfy.
i. vertical formwork to columns, walls, beams - 16
to 24hrs
ii. Soffit formwork to slabs(props to be refixed
immediately after removal of formwork) - 3 days
iii. Soffit formwork to beams(props to be refixed
immediately after removal of formwork) - 7 days
·
props to slabs:
a) Slabs spanning up to 4500 mm - 7 days
b) slabs spanning over
·
props to beams and arches:
a) Beams spanning up to 6000 mm - 14 days
b) beams spanning above 6000 mm -21 days
ROOF LEVEL CONCRETE.
Floor shuttering levels to be as per architectural drawings.
The shuttering should be leveled and contain no voids to prevent slurry
leakage. The external shuttering to be more in height by 75 mm than required. Diagonals
of each rectangles / squares shall be checked.
·
distribution reinforcement for slab top
rods shall be y8@225cc unless specified otherwise in relevant drawing pin
rods/chairs
·
Second layer and third layer
reinforcement in beams to be tied with pin rods of y20 / y25 only.
·
chairs to be provided to support top
reinforcement in slabs using suitable dia bars with approval of engineer in-charge
CONSTRUCTION JOINTS
·
Construction joints in slabs and beams
are often placed either at point of contraflexture in which case the concrete
may be left sloped off or stepped off by means of stop forms. Construction
joints located near minimum shear shall have stop forms perpendicular to the
acting forces. Where the concrete is to be placed in the second pour, the old
concrete shall be thoroughly roughened to expose aggregates. Moistened and a
layer of rich fresh mortar should be laid immediately before fresh concrete is
placed. it should be placed to a thickness of 20 to 30mm and shall be worked
well into the irregularities of hardened concrete.
·
All the construction joints shall be
pre-determined as per the sequence of operation and shall be got approved.
·
Construction joints shall be in
accordance with typical construction joint details.
·
Expansion joint detail shall be as per
typical expansion joint details.
CURING METHOD
·
Curing of slabs and beams shall be
achieved by ponding only, for a minimum period of 7 days.
·
Curing of footing tops, rcc walls,
columns and external beam faces shall be done by covering them with gunny bags
or hessian and keeping wet constantly for complete curing period of 7 days.
·
Groove cutting machine shall be used for
chasing of walls for all electrical conduits.
·
4" wide to 7" wide expanded
metal mesh shall be used before plastering of all conduit chasings in walls.
·
For column-wall junctions &
beam-wall junctions 4" wide expanded metal mesh shall be used, before
plastering of concrete and wall junctions.
WATER RETAINING STRUCTURE
·
Concrete mix m-25 shall be used for all
water retaining structure with 330kg/cu.m of cement minimum. Unless otherwise specified.
·
ditchtment d.m or conplast liquid
admixture shall be used with m-25 concrete at 150 ml per bag of cement.
·
Plastering shall be done with c.m 1:4
using putz ditchment d.m or conplast liquid admixtures at 150ml per bag of
cement.
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